The present invention relates generally to equipment utilized in, and operations performed in conjunction with, subterranean wells and, in an embodiment described herein, more particularly provides a subsea test tree.
Blowout preventer (BOP) stacks used in drilling and completing offshore and other underwater wells have become increasingly compact. For example, it is no longer uncommon for a BOP stack to have only about four feet or less vertical space between multiple shear rams and multiple pipe rams. With a conventional subsea test tree positioned within such a compact BOP stack during drill stem testing, it may not be possible for each of the pipe rams and each of the shear rams to successfully close.
If one or more of the pipe rams is not permitted to successfully effect a seal on the subsea test tree, or on a tubular string in which it is interconnected, fluid communication may be allowed between an annulus above the pipe rams and an annulus below the pipe rams. If one or more of the shear rams is not permitted to successfully close and shear the subsea test tree, or a tubular member attached thereto, it may not be possible to completely shut in the well. Thus, it will be readily appreciated that it would be highly advantageous for a subsea test tree to permit closing of multiple pipe rams, and to permit closing of multiple shear rams, while the test tree is operatively positioned within a compact BOP stack.
In order to accomplish this result in a compact BOP stack, a portion of the subsea test tree should be configured and dimensioned appropriately to permit sealing engagement of pipe rams therewith. Another portion of the subsea test tree should be configured and dimensioned to enable it to be positioned axially between the pipe rams and the shear rams. When closed, the pipe rams could seal against the appropriately configured portion, and the shear rams could sever another tubular member, such as pipe, extending outwardly from the portion of the subsea test tree positioned between the pipe and shear rams.
From the foregoing, it can be seen that it would be quite desirable to provide a subsea test tree which is usable within a compact BOP stack, permits sealing closure of multiple pipe rams therewith, and which permits a portion thereof to be operatively positioned within the BOP stack axially between multiple pipe rams and multiple shear rams.